Diabetes Mellitus is a common metabolis disorder in which vascular abnormalities involving large as well as small blood vessels contribute significantly to morbidity and mortality. It is hardly surprising, therefore, that several striking hemodynamic disturbances regularly accompany the progression of the diabetic state, with the kidney being a particularly vulnerable organ for injur. At the microcircularoty level, these vascular disturbances include alterations in capillary and precapillary vasomotion, microaneurysms, endothelial cell proliferation, alterations in blood volume and baro-receptor activity and altered responsiveness to a variety of neurohormonal substances. Maintenance of circulatory homeostasis depends to a major extent on the responsiveness of the microcirculation to angiotensin II and sympathetic neurohumoral factors. The technique of in vivo micropuncture will be applied to the present study to evaluate glomerular hemodynamics in the diabetic rat. The results to be obtained are likely to shed new light on the mechanisms responsible for the altered vascular reactivity characteristic on the diabetic state. These micropuncture measurements will be combined with rigorous in vitro studies designed to analyze the kinetics of vasoactive hormone binding to glomerular receptors.